1. Field of the Invention
The present invention relates to an image forming system, particularly to an image forming system including a stencil printer or other such image forming apparatus and any of various sheet after-processing apparatuses connected to the image forming apparatus.
2. Description of the Related Art
Sheet after-processing apparatuses that are combined with an image forming apparatus such as a stencil printer to constitute an image forming system include, for example, sorters for collating and stapling the printed sheets after printing. Among the operating modes using a sorter are included:
(1) Sort mode in which printed sheets are successively sorted by page into multiple sorter bins to produce printed documents, pamphlets, books or the like. PA1 (2) Group mode in which multiple documents are sorted into groups and stored in bins to carry out multiple sorting by document of (sheets.times.groups). PA1 (3) Dry mode in which printed sheets are sequentially distributed into multiple bins one by one to reduce the amount of transfer printing to the backs of the overlaid sheets. PA1 an image forming apparatus for forming desired images on sheets and discharging the image-formed sheets, PA1 a sheet after-processing apparatus connected to the image forming apparatus and capable of after-processing the image-formed sheets discharged from the image forming apparatus in any of multiple operating modes, PA1 mode selection means for selecting a sheet after-processing operating mode of the sheet after-processing apparatus, PA1 detection means for detecting presence of sheets stored in the sheet after-processing apparatus, and PA1 control means responsive to detection by the sheet detection means of presence in the sheet after-processing apparatus of sheets stored in a certain mode for disabling operation of the image forming apparatus when an operating mode using the sheet after-processing apparatus that is different from the certain mode is selected by the mode selection means. PA1 an image forming apparatus for forming desired images on sheets and discharging the image-formed sheets, PA1 a sheet after-processing apparatus connected to the image forming apparatus and capable of after-processing the image-formed sheets discharged from the image forming apparatus in any of multiple operating modes, PA1 mode selection means for selecting a sheet after-processing operating mode of the sheet after-processing apparatus, PA1 detection means for detecting presence of sheets stored in the sheet after-processing apparatus, and PA1 notification means responsive to detection by the sheet detection means of presence in the sheet after-processing apparatus of sheets stored in a certain mode for issuing an error notice when an operating mode using the sheet after-processing apparatus that is different from the certain mode is selected by the mode selection means.
Operation is also possible in a non-sort mode in which printed sheets are discharged directly onto a sheet output tray without being collated. As the sheet output tray is attached to the image forming apparatus, the non-sort mode can be used to conduct image forming operation even when the sorter is inoperable. Stapling is an operation ordinarily conducted in sort mode.
One problem with such a sorter is that after a first batch of printed sheets has been sorted in one mode, a second batch may be sorted on top of the first in another mode. For instance, printed sheets may be sorted in group mode on top of printed sheets collated in sort mode. This makes the collated printed sheets useless and also causes them to get mixed in with the printed sheets sorted on top of them and the operator has to go to considerable extra work to separate the printed sheets manually.
When an error arises in the sorter, such as when the sorter door is not properly closed, the sorter remains inoperable even after sort mode is selected. To conduct printing, therefore, it is necessary to change the selected mode to one that does not use the sorter, i.e., to non-sort mode.